Scientists explain ancient Rome's long-lasting concrete

Adam Taggart
By Adam Taggart on Tue, Jul 4, 2017 - 3:00pm

Believe it or not, it has taken science two thousand years to finally unlock why the type of concrete used by the ancient Romans has been able to last so long compared to our modern version:

Scientists explain ancient Rome's long-lasting concrete

Ancient sea walls built by the Romans used a concrete made from lime and volcanic ash to bind with rocks.

Now scientists have discovered that elements within the volcanic material reacted with sea water to strengthen the construction.

They believe the discovery could lead to more environmentally friendly building materials.

Unlike the modern concrete mixture which erodes over time, the Roman substance has long puzzled researchers.

Rather than eroding, particularly in the presence of sea water, the material seems to gain strength from the exposure (...)

The ancient mixture differs greatly from the current approach. Modern buildings are constructed with concrete based on Portland cement.

This involves heating and crushing a mixture of several ingredients including limestone, sandstone, ash, chalk, iron and clay. The fine material is then mixed with "aggregates", such as rocks or sand, to build concrete structures.

The process of making cement has a heavy environmental penalty, being responsible for around 5% of global emissions of CO2.

So could the greater understanding of the ancient Roman mixture lead to greener building materials?

Prof Jackson is testing new materials using sea water and volcanic rock from the western United States. Speaking to the BBC earlier this year, she argued that the planned Swansea tidal lagoon should be built using the ancient Roman knowledge of concrete.

"Their technique was based on building very massive structures that are really quite environmentally sustainable and very long-lasting," she said.

The full BBC article can be read here.

The findings above add further validation to PeakProsperity.com's warnings about the dire state of the vast percentage of concrete structures (buildings, bridges, roadways, airports, etc) our society depends on. Many of these are literally crumbling before our eyes and will need to be replaced/rebuilt in just the next few decades -- an immensely expensive undertaking, both financially and energetically.

If you have yet to already, be sure to read our report Our Future Is (Literally) Crumbling Before Our Eyes.

11 Comments

Mike Dill's picture
Mike Dill
Status: Bronze Member (Offline)
Joined: Nov 8 2009
Posts: 28
Most of our concrete problem is rebar

Most of the reinforced concrete used in our roads, bridges, and buildings, is reinforced with cheap steel rebar. The problem is that the steel expands as it oxidizes. That cracks the cement from the inside. There is a new carbon fiber 'rebar' that does not have this problem, and will allow the concrete to last much longer in the prescence of any oxidixing agent, including sea water.  

KugsCheese's picture
KugsCheese
Status: Diamond Member (Offline)
Joined: Jan 2 2010
Posts: 1428
Concrete Boondoggle

Using proven techniques would ruin the road/sidewalk/embankment stimulus program that requires constant repair and replacement after ten years.

ezlxq1949's picture
ezlxq1949
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Posts: 174
Concrete Solutions

Interesting article from the BBC.

We've known about pozzolano for decades — I was lectured on it at university 45 years ago and the 1911 Encyclopaedia Britannica provides a vague formula: "Pulvis Puteolanus mixed with lime".

But now we have a more detailed analysis which promises more durable concrete. The Romans didn't use steel reinforcing and this limited the size of their suspended structures, e.g. the Pantheon roof. Stainless steel reinforcing might not rust but it seems a bit of a Rolls-Royce solution to the corrosion problem.

Now to ransack the planet for the vital ingredients. Oh dear...

LesPhelps's picture
LesPhelps
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Posts: 728
And Yet Rome Fell

"All that exists passes away."

I realize that our concrete is a major infrastructure problem.  It would be nice if our bridges and windmills would last 500 years.

However, I will not miss many of the things we make out of concrete.  Strip malls come to mind.  Also, Walmart Super Centers simply don't compare to the Parthenon. smiley

 

ezlxq1949's picture
ezlxq1949
Status: Silver Member (Offline)
Joined: Apr 29 2009
Posts: 174
Concrete Jungle

Agree. I am torn between wanting our modern structures to last 500 years — a good investment — and having them crumble away in a decently short (define) amount of time. Even a minor building or planning mistake can take 50 years to correct; a major mistake hundreds.

The way concrete is used in our era creates buildings that are just plain ugly. I have yet to encounter examples of (New) Brutalist architecture that give me that warm and fuzzy feeling.

There are a number of concrete-based road bridges around where I live. Not so long ago a number of them got added reinforcing after only 20 years of use. So soon...

(BTW, it's Pantheon not Parthenon.)

LesPhelps's picture
LesPhelps
Status: Platinum Member (Offline)
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Posts: 728
ezlxq1949 wrote: (BTW, it's
ezlxq1949 wrote:

(BTW, it's Pantheon not Parthenon.)

Outside of my realm of expertise.  Parthenon = Greek, approx. 450BC;  Pantheon = Roman? approx. 150AD.  I couldn't tell you if either of them had any concrete, or were entirely stone.  Both held up better than what we are building.

I mostly remember the Parthenon because of Howard Roark, not exactly credible knowledge.

 

Tycer's picture
Tycer
Status: Platinum Member (Offline)
Joined: Apr 26 2009
Posts: 601
ezlxq1949 wrote: Stainless
ezlxq1949 wrote:

 Stainless steel reinforcing might not rust but it seems a bit of a Rolls-Royce solution to the corrosion problem.

Stainless steel loses its stainless properties in the absence of oxygen and will rust rapidly in salt water and concrete.

I like the carbon fiber idea.

Greg H's picture
Greg H
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Joined: Jul 25 2012
Posts: 1
LesPhelps wrote: However, I
LesPhelps wrote:

However, I will not miss many of the things we make out of concrete.  Strip malls come to mind.  Also, Walmart Super Centers simply don't compare to the Parthenon. smiley

 

Many of the retail buildings you see (I'm thinking of the freestanding drugstores that have bloomed all over the country in the past couple decades) are engineered to last 20 years and then be torn down.  In many cases, the company that owns the building and operates the store, does not own the land underneath, but has a 20 year lease.

 

So, you lease the land for 20 years, put up a 20 year disposable building, and in 19 years re-evaluate the local market.  If it's good, renew the lease and put up another disposa-store, otherwise walk away.  The exact opposite of the Roman focus on durability.

gyrogearloose's picture
gyrogearloose
Status: Platinum Member (Offline)
Joined: Sep 8 2008
Posts: 537
Rebar corrosion

Properly made concrete inhibits the corrosion of steel as it has a high pH.

However there are subtleties in the picture.

The thickness of concrete between the steel and the atmosphere is important as gases can penetrate the concrete through micro cracks and a reduce the pH around the steel, and the thicker the concrete cover is the slower this happens. 

In New Zealand when building a residential structure, the steel must have at least 50mm cover, as this results in a 'sufficiently' long life structure.

 

If the contractor fails to follow the plans and through shoddy workmanship or any other reason, and the concrete cover is much less the steel will rust and spall off the concrete in a much shorter time frame. ( the depth:lifespan relationship is not linear)

So a cheaply made structure ( made according to plan with say a 25mm min cover maintained ) will not last long, where as one made with 50mm cover will last a pretty good time, and one with a minimum of 100 mm cover will waaaayy longer. ( but 100mm cover costs more.... )

You get what you pay for....... unless someone cheats!

A bridge I pass over close to home is over 100 years old and shows no sign of rebar corrosion yet.

yet In the USA you have modern motorway bridges already in poor repair from this problem.....

Regards Hamish

nigel's picture
nigel
Status: Silver Member (Offline)
Joined: Apr 15 2009
Posts: 138
Basalt Rebar

I'm going to start foundations on my new house next year, and I've been reading up on alternatives. Bamboo has been trialed, and the one I'm most interested in is re-constituted basalt.

http://basalt-rebar.com/

 

Mike Dill's picture
Mike Dill
Status: Bronze Member (Offline)
Joined: Nov 8 2009
Posts: 28
The Pantheon and the Roman Colliseum

I was looking at the picture you used for the article, and it reminded me that the Colliseum was mostly built of tile with a concrete mortar. The reason why some of it is missing is that the tiles were taken for use elsewhere. This is the reason why a lot of the old Roman buildings are in disrepair.

The Pantheon, which is nearby but elsewhere in Rome, is a compression structure, not needing much tensile strength. If built properly, most compressive structures last nearly forever. Tensile structures, which have a tendency to 'pull apart' are better built of other materials, but often concrete is used because it is cheaper.

The first iron railway bridges failed, as iron also has a poor tensile strength. Arches provide compression along the arch, which allows stone and concrete structures made that way to last a very long time. Flat spans of un-reinforced concrete and stone are very weak.

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